What is Ideal Gasket Stress?

March 26, 2020

By: Samantha Harrison, Lab Testing Technician/QA Assistant

Gasket stress is a very important parameter that describes the unit load of a bolted joint surface because each type of gasket material responds differently to gasket stress. Soft and conformable gaskets may seal at low gasket stress where hard metal gasket may require much higher stress. It is always important to contact gasket manufacturers to determine the recommended gasket stress and/or how the gasket will react with the load that is available.

There are 4 aspects to gasket stress


1. Conforming to flange surface

A flange surface will never be perfect. There could be pitting or corrosion that affects the surface, requiring the gasket to have enough compression to form and fill the voids.

2. Block the gaskets material permeability

The gasket needs to be able to block any permeability in the gasket body. The permeability through gaskets are different for each material. The rate of leakage decreases as the compressible load increases. The required stress is dependent on the permissible leakage requirements determine by the end user, such as a T3 tightness level (0.00002 mg/sec/mm-dia).

3. Withstand internal pressure

The gasket needs to be able to withstand internal pressures acting upon it. The minimum compressive stress needs to be high enough to maintain the friction that is needed to keep a gasket from blowing out. This is more common for non-metallic gaskets that has internal pressures that are dependent on friction.

4. Temperature

Temperature is an important factor when determining gasket stress. When temperature is elevated it will cause gasket relaxation and relaxation in the bolt load. When installing the gasket, it needs to have a high enough stress that will compensate for this. Therefore, it is always important to retorque the gasket 4 to 24 hours at ambient temperature after installation.

There are different types of stresses that occur in a system; minimum seating stress, ideal operating stress, minimum operating stress and maximum operating stress specific to a given gasket material. The values for these stresses can be found in ASME PCC-1.

  • Minimum Seating Stress
    Occurs when there is an assumption of little or no pressure for the gasket to be able to conform to the flange.
  • Minimum Operating Stress
    This is dependent on the design pressure of the assembly.
  • Maximum Assembly Gasket Stress
    Is the stress that could damage the integrity of the gasket to affect the ability to maintain a seal.

The target stress to be used will allow for optimal performance and sealability. This will be at a value that is not too high to cause damage to the gasket but at the same time, allow enough load to the gasket.

It is always important to properly install a gasket. If done correctly, with adequate gasket stress and proper procedures, be assured that the gasket is given the best chance for a leak free service life.

Learn more about Gasket Installation Procedures.

Packaging and Handling SWGs

February 28, 2020

By: Samantha Harrison, Lab Testing Technician/QA Assistant

Spiral wound gaskets (SWGS) are a multi-component product that needs to be handled with care to prevent damage to the gasket. So it is very important to take great pride in packaging these SWG’s so that they reach our distributors safely and intact.


Most gaskets, including SWGs can be used safely after being in storage for years. SWGs should not be exposed to extreme temperatures, humidity, ozone and UV when being stored. These can cause accelerated deterioration of the gasket. Ideally some storage tips are:

  • Store in a cool, dry place
  • Do not expose gasket to excess heat or humidity or extreme fluctuations of heat and humidity
  • Keep gaskets clean and free of mechanical damage
  • Prevent dust and particulate damage
  • Avoid hanging gaskets


  • Keep gaskets flat or adequately supported to avoid any distortion
  • Extra care should be taken when handling large SWGs greater than 500mm (20”) in diameter
  • For SWGs that are greater than 800mm (32”) we recommend additional hands in order to properly support the gasket
  • Always wear gloves when handling SWGs and do not hold the inner or outer ring only

When handling a SWG it is always important to handle the SWG by the outside of the gasket instead by the center winding of the gasket. When held by the center or winding it could cause the gasket winding to pop…. So, don’t do that!


  • When packaging smaller gaskets, it is common to package 10 to 20 gaskets together with spacers attached to help prevent inner ring popping. These spacers can be re-used and cut down when storing or re-shipping smaller stacks of SWG’s.
  • Then the gaskets are shrink-wrapped.
  • Large gaskets 20” in diameter normally come singular and are attached to a piece of cardboard to keep them ridged
  • It is common for the sealing to become dislodged from the centering ring. In most cases they can be reassembled with a little bit of patience.

Watch this short video showing a re-assembled SWG.

Remember that SWGs are made of multiple components and need to be packaged well in boxes. If boxes rattle, the packaging is no good.

What is m and y gasket design constants, and how are they used?

December 3, 2019

By: Samantha Harrison, Lab Testing Technician/QA Assistant


m & y explained

Gaskets are designed to maintain a static seal between two stationary, imperfect surfaces of a mechanical system and must be able to maintain that seal under different operating conditions, such as temperature and pressure.

The design of bolted flanges requires that gasket constants referred to as m and y be used in the calculation when determining the right gasket for a flanged joint. The gasket must be able to conform to the flange surface and compress enough to seal any voids or spaces. m represents the maintenance factor and the y represents the seating stress.

y is the minimum compressive stress on the contact area of the gasket necessary to provide a seal at an internal pressure of 2 psig and applied to compress the voids of the gasket to conform to the flange surface.

The flange designer uses the m value as a multiplier factor to determine the compressive load on the gasket required to maintain a seal when the vessel is pressurized. This constant is intended to ensure that the flange has adequate strength and available bolt load to hold the joint together, while withstanding the effects of hydrostatic end force or internal pressure.  The forces from proper bolting will keep the flange together under pressure and exert additional stress on the gasket m multiplied by the internal force. Then the designer calculates the load required to seat the gasket and performs a second calculation using the m value and the design internal pressure. The flange will be made based on the larger of the two values.


Mechanical solutions are generally rigid coverings or clamp encapsulated to the flange or the void between the flanges. These covers and clamps are made from stainless steel or plastic and incorporate a rubber seal.

It is common to use ASTM F586 as a guide to test these values. Ultimately the m factor is the additional preload needed in the flange fasteners to maintain the compressive load on the gasket after the internal pressure is applied to the joint. The dimensionless m value is calculated by dividing the net pressure from the internal pressure.

In service the initial compression of the gasket is reduced by the internal pressure acting against the gasket (blowout pressure) and the flanges (hydrostatic end force). The additional preload needs to be accounted for. The m was created by the ASME to account for this preload. The m factor determines how many times the residual load (original load minus the internal pressure) must exceed the internal pressure.


Critical Considerations

To prevent leaks and injuries it is always important to consult with the manufacturer to determine the m and y factors for the gasket material being used. If the m or y factor cannot be met it will cause an imperfect seal and the gasket design will need to be changed. Often the change can be made by decreasing the surface area of the gasket or by using a thicker gasket. Often thicker gaskets can be unsatisfactory for a long-term solution.

The ASME has developed new gasket design factors for the bolted joint designs where it is important that a desired level of tightness be achieved. The downside to m and y factors is that they do not take fugitive emissions into account, whereas the new assumption is that all bolted joints leak to some extent.

Another consideration to understand is that their m and y constants do not address joint tightness and do not consider potential joint relaxation due to temperature effects, torque scatter and inherent inaccuracies involved in assembly.


Since there is currently no industry standard test to determine the m and y gasket constants, many gasket manufacturers have developed individual test procedures based on the ASTM F596 test method. There is also no approved ASME alternative to the code that requires use of these constants.


For more information on this topic, read about gasket fundamentals and installing a gasket.

How to Avoid Corrosion on Flanges

October 7, 2019

By: Samantha Harrison, Lab Testing Technician/QA Assistant

Shutdowns cost industry millions. And a significant impact on operating costs can be due to corrosion, or damaged flange faces. When corrosive media meets the sealing surfaces of facing flanges a leak WILL occur. So, flange maintenance is an important step to help prevent leakage.


Flanges can go through two types of corrosion in their lifetime; Pitting and Crevice. Pitting Corrosion occurs on the flange face and often appears in clusters or groups. This type of corrosion causes small cavities, or pits, to form on the surface of a material. Pitting corrosion is best prevented by proper alloy selection. See Pitting Resistance Equivalence Number (PREN). The very high rate of Crevice Corrosion occurs when there is a build-up of concentrated substance between two adjoining flanges. This type of corrosion can be very damaging because it is not easy to inspect the areas where it is occurring.


Currently, the method of monitoring flange damage is to disassemble the joint and visually inspection of the surfaces. This is not ideal due to down time and cost. There has been some development with using some non-destructive techniques to inspect the amount of corrosion to the flange.


Prevention methods

Maintenance paints is the most common method to prevent corrosion. Maintenance paints are commonly epoxy- or urethane- based. Most maintenance paints will bond directly to the substrate as a hard coating. When using maintenance paints there must be a perfect amount applied, if the paint is too thin, the area will be ineffective and if the paint is too thick, it will cause seizing to the fastenings. Since there are lots of different angles and flange shapes, you may not be able to coat the whole area. After the flange is inspected, another layer of coating may need be applied. A benefit to using maintenance paints is that it does not require hot work or specialist equipment.


Mechanical solutions are generally rigid coverings or clamp encapsulated to the flange or the void between the flanges. These covers and clamps are made from stainless steel or plastic and incorporate a rubber seal.


Another solution is the usage of tapes or semi solid tapes. Tapes can be composed of petrolatum, wax, or visco-elastic polymers embedded into fabric for wrapping. These are used specifically for their water-repellent nature of semi solid polymers.


All the preventative methods have some pros and cons. There is no solution out there to completely prevent corrosion from happening, but regular maintenance and inspections can help prevent rapid corrosion.


4 Ways to Repair Corroded Flanges

  • Remove the damaged flange and weld on a new one
  • Machine the sealing face or ring grove within the flange tolerance
  • Add material to sealing face or ring grove and then machine within flange tolerance
  • Add a polymer composite to rebuild the flange face


3 Factors to Influence Corrosion Resistance During Operating Conditions

  • Corrosive agent concentration
  • Purity of corrosive agent
  • Temperature of corrosive agent (the higher the temperature the more rapid the corrosion)


Some flange materials are subject to stress corrosion cracking. This fact must be considered when selecting the gasket type and material. When a proper gasket is selected it can help prevent flange corrosion from aggressive chemicals.


There are also different type of flange faces and the gasket needs to adhere to the proper type of flange face. When dealing with chemical oxidizers/HF acid it is important to select a strong gasket that will prevent corrosion. Chemical oxidizers/HF acid do well with raised faced flanges and a PTFE gasket for a class 150. It also does well with Spiral wound gasket with a graphite or PTFE filler at class 150, 300 and 600.  PTFE can handle most of the stronger oxidizers if the temperature is below 260°C. Modified PTFE also works because it is chemically inert and stable.


As a preventative solution on plant equipment and to prolong its life and avoid costly shutdowns, using recommended torque values and proper bolting techniques when installing a gasket and regular inspections can prevent rapid corrosion from happening.

2018 Randy McKay Sales Award goes to…..

“The Randy Mckay award is given out annually by Triangle Fluid Controls to the Regional Sales Manager with the highest year over year growth in their respective territory. I am pleased to announce this years winner, our Western Canada Regional Sales Manager, John Anderson. John has been with our organization for over 10 years and brings with him more than 30 years of industrial sales experience. Please join me in congratulating John on his achievement!” – Mike Boyd, TFC General Manager.

The award, created in memory of the late Randy McKay, TFC’s Central Canada RSM, was created by TFC President Mike Shorts, as a means of paying homage to the former TFC employee. “Randy did a lot for TFC, was a stand-up individual, and somebody that I personally, learned a lot about sales from. After Randy’s passing in 2015, I knew I wanted to create an award in his memory.”

The award includes two pieces: an engraved glass plaque and hand-blown glass sculpture made in a similar shape, style, and colouring to TFC’s company logo. The glass plaque will hang in TFC’s lobby with each year’s winner added to it. The making of the pieces, commissioned by a local glass blower in Wellington, Prince Edward County, and was completely documented and can be found posted online on TFC’s social media channels or by clicking here.

Benefits of Flexible Graphite

August 21, 2019

By: Michael Pawlowski, Laboratory Technologist


Because of its versatility and sealing capabilities, Flexible graphite is becoming a favourable material for extreme service applications. From pulp and paper, and mining to chemical, petrochemical, and automotive applications, the high thermal conductivity, chemical resistance, and self-lubrication of flexible graphite lends itself well in these industries. The chemically inertness (apart from strong oxidizers) allows for the operation in a pH environment of 0-14. In addition, graphite offers high thermal conductivity and low electrical resistance.

Flexible graphite is particularly attractive to the textile industry, as it is non-hazardous and conforms to both the registration, evaluation, authorization and restriction of chemicals and hazardous substances.

Flexible graphite sheet, made from mineral expandable flake graphite, contains a carbon content between 95 and 99 percent. The flexibility of the graphite sheet is directly proportional to the carbon content.



Typically, oxidative effects begin to appear around 450℃ (in atmosphere) and the graphite will start to degrade. However, additives like ceramics, and silicon may be used to reduce oxidative stress and increase the operational temperature.

Characteristics and Benefits:

  • Asbestos-free and contains no fibers, binders or additives
  • Impermeable to gases and liquids
  • Suitable for service over a wide range of pressures and temperatures
  • Resists thermal shock
  • Maintains excellent seal ability
  • Does not age, shrink or harden
  • Seals easily under low to moderate bolt loads
  • Highly chemical resistant

Durlon® Flexible Graphite is available in several variations. These include homogeneous sheet and laminated styles with various types of core materials. Because Flexible Graphite exhibits low electrical resistivity and high thermal conductivity, it is suitable for cryogenic temperatures and other applications; automotive, refining and petrochemical plant processes.


Why use Flexible Graphite?

A typical high-temperature application is considered to hover around 370-425℃. For extreme and super-heated steam applications, that number reaches up to 538℃. At these temperatures, graphite can actually oxidize and become powder in a matter of seconds if operation in an oxygen-enriched environment. Therefore, gaskets for extreme temperatures must be protected.

With the appropriate sealant enabling it to withstand harsh conditions, flexible graphite remains unaffected by exposure to heat across a wide temperature range; this makes it the go-to material for high-temperature gaskets.

Triangle Fluid Controls Ltd. manufactures a Flexible Graphite sheet capable of retaining dimensional shape and will maintain an excellent seal under extreme pressures and high temperatures while most Flexible Graphite sheets are generally inflexible, rigid, and have higher leakage rates due to graphite oxidizing at lower temperatures because of impurities found in the material.

Our Durlon® Flexible Graphite sheets can be cut into any shape and size, allowing us virtually unlimited gasket capabilities.


How to Manage and Understand Flange Face Damage

July 31, 2019

By Chett Norton, C.E.T.

Many of the aging plants we service are run beyond their expected life cycle and over time, metal piping, including flanges can corrode and become worn due to various reasons, making flange conditions a very important part of creating an effective gasket seal.

One of the main reasons that flanges become damaged is due to gasket removal techniques. A lot of time, fibre-based gaskets or even graphite from spiral wound gaskets can become stuck to the flange or embedded into the flange sealing serrations. Installers will try to remove the gaskets or debris using a chisel and hammer, scrapers, or even grinding them off. These methods are all very bad and can create more harm than good as they can lead to defects on the sealing surface in the form of pits, gouges or even deep scratches.

Now I will say that there are some good technologies out there, from anti-stick coatings to anti-adhesion release technologies. But, because all gaskets do not stick the same, adhesion testing data should be looked at as well when considering the correct material.

Gasket manufacturers will always give minimum recommended seating stress for each gasket material to ensure that when tightened to the proper load, the gasket forms into the serrations on the flange, preventing it from being blown out (trying to overcome the forces of system pressure and hydrostatic end force). What this minimum gasket load doesn’t account is the appearance of any flange defects or irregularities mentioned above. This is when gasket thickness and material properties become very important. Ideally when the gasket is compressed to the recommended load, it should densify enough to prevent permeation of the media through the gasket, fill the serrations of the flange and any imperfections on the sealing surface. Failing to fill these imperfections or defects will create a leak path, resulting in an undesirable situation.

The gasket thickness chosen for your application should always be as thin as possible because gasket creep/relaxation is linear to the thickness of the material. So, the thicker the gasket material, the more potential for gasket creep/relaxation.  In industry, the most common thicknesses used for soft gaskets are 1/16” (1.5mm) and 1/8” (3mm). In a perfect world, using 1/32” (0.8mm) would be ideal however due to flange serrations and any imperfections on the sealing surface, there might not be enough material to fill these defects when compressed.

So now I am going to pose the question, how much is too much damage on my flanges? Honestly the answer is: It depends! What I strongly recommend is to always reference ASME PCC-1 (a post-construction standard for bolted flange joint assemblies). It is a very useful document when trying to determine how much, is too much damage, specifically Appendix D – Guidelines for allowable gasket contact surface flatness and defect depth. This document references allowances for flange face flatness, flange face imperfection tolerances and allowable defect depth vs. width across face for both hard gaskets (semi-metallic or metallic) and soft gaskets (fibre-based and PTFE). And also provides a Flange Damage Assessment for Pits & Dents and Scratches & Gouges. So basically, a “go” and “no-go” verification of what is allowable or not. As a precaution, I do want to add, just because the damage is within acceptable ranges, proper gasket selection is critical to achieving an effective seal.

Tips for preventing premature flange damage:

  • Never use a chisel, screwdriver, scraper or grinder to remove gasket debris from the flange surface. Using a soft wire brush made from a softer material than the flange itself is ideal, e.g. Copper.
  • Choose a gasket material that has good anti-stick properties.
  • Proper gasket thickness, hardness and material compressibility based on the conditions of the flange all need to be taken into consideration. The standard big 3 factors; PxTxM (Pressure, temperature and media) will ensure you are filling all the defects in the flange sealing face.
  • Visual inspections of both the gasket and the flange after removal will let you know if the gasket selected is doing its job. If the material or installation method is sub-par, this may cause the media to seep between the gasket and the flange (tangential leakage) and can cause premature sealing face corrosion and furthermore, defects or sealing face issues.

Remember, there is no perfect material to fix bad flanges, so taking care of them is your best defense!

For other specific applications or general procedures, please contact the TFC applications engineer at [email protected] and you can read more about our Gasket Installation Procedures here.

Until next time, remember to always “Keep the fluid between the pipes”.


Benefits of Replacing a Swing Check with a Non-Slam Check Valve

July 3, 2019

By: John Anderson

Recently, while calling on an oil and gas customer, I was illustrating the perils of using a swing check on liquid pump discharge where reverse flow and water hammer can be an issue. Part way through our conversation, the customer’s eyes lit up, and he said, “oh, that’s why I found the disk of the check valve in my sump!”. That is one of the risks that designers and maintenance people run into, when a swing check valve is misapplied on pump discharge where reverse flow and water hammer can be a problem.

When a pump trips, (due to a power failure as an example), backflow can get into the pump discharge, spinning the impellor of the pump the wrong way, and potentially damaging the pump. A check valve is typically applied to the pump discharge, to prevent this from occurring.

In a situation, that I term “light duty”, meaning that the pump is not cycling often, and there is not a large volume of media at play, (water as an example), a swing check would likely be fine in that application. However, in a situation where the pump is cycling often, and is dealing with a large volume of fluid (horizontal orientation), several things can happen, if a swing check is misapplied in this case.

Due to a phenomenon known as column separation, an inordinate amount of head comes back onto the pump when it trips. In this case, a swing check does not close quickly enough to prevent backflow from getting past the valve, and when it closes, it slams shut, and backflow behind the valve hits the disk, the energy has to dissipate somehow, and it does so in the form of water hammer. This occurs because a swing check largely depends on back flow for it to close. A non-slam check valve does not. It utilizes a coiled spring, downstream from the valve disk, that moves the disk toward the seat as soon as the flow velocity slows down. This valve is designed to be closed, just before zero flow is reached, thereby eliminating backflow. With no backflow, the cause of the water hammer disappears.

In addition, if a misapplied swing check sees a number of slamming incidents, it is possible for the hinge pin (holding the valve disk in place), to crack, and break off, thereby sending bits of metal downstream, potentially damaging components downstream of the check valve. It is also possible for the entire disk to break off, sending it downstream, leaving nothing but a spool piece.

Designers and maintenance personnel should be aware of situations where backflow and water hammer can be a problem on pump discharge and consider the use of a non-slam check valve in these cases, thereby eliminating the chance that you to may find a disk in your sump!

As the Canadian distributor of DFT® silent check valves, Triangle Fluid Controls Ltd. is proud to represent a company that is known around the world as the valve to use for preventing or eliminating Water Hammer problems – DFT® Check Valves, Serious performance, Superior reliability.

Gasket Joint Safety

June 24, 2019

By: Samantha Harrison, Lab Testing Technician/QA Assistant

Safety First

Being safe on the job includes maintaining and correctly installing gaskets. The number one safety procedure when installing a gasket into a bolted flange joint is to have an assembler who has been qualified in reference to ASME PCC-1. When installing a gasket, make sure proper PPE (personal protective equipment) is worn. This can include safety glasses, hard hats, steel toed shoes/boots, gloves, etc. Proper lockout and tag-out procedures also need to be followed. And it is critical to check that there is no debris, or foreign material on the sealing surface in order to avoid leaking of fluid and gases. Choosing the right gasket is imperative for safety. If a gasket is not the right size or material it can result in leaks, serious damages and ultimately, injury.

Considerations for Bolted Flange Connections:

  • temperature and pressure of the fluid
  • chemical nature of the fluid
  • mechanical loading
  • variations of operating conditions

Different stress variables need to be analyzed when choosing a gasket. This includes minimum seating stress, ideal operating stress, minimum operating stress and maximum operating stress. All these variables need to be understood and taken into consideration. It is always advised to purchase gaskets from a reputable supplier whose priority is to sell quality products and back it up with technical support.

Always make sure that the material of the gasket is compatible with your application. If a gasket is deteriorating it most likely means the material is incompatible with the fluid and temperature. When a gasket deteriorates it can cause leakage which can lead to damages and injuries.

You should never re-use a gasket because it will affect its mechanical properties. As a system expands and contracts, the gasket should move with the piping. If it doesn’t and there isn’t enough load on the gasket you will get a leak which can lead to serious injuries.

When installing a gasket, it is imperative that proper bolting procedure is followed, such as the modified legacy method (star pattern) mentioned in ASME PCC-1. Without proper bolt tightening, leaks can occur resulting in damages and serious injuries. The operating temperature should never be exceeded above the maximum allowable temperature. If the temperature is exceeded it can cause heat cracks and blistering which can inevitably cause leakage.

When disassembling a joint it is important that proper plant procedures are in place. The procedure should include lockout and tag-out to depressurize the system, removal of liquid head from the system. Always loosen the joint away from yourself in case of accidental release.

Here are important questions to ask yourself before disassembling:

  • Is the flange still under pressure?
  • Is there still gas or fluid in the line?
  • What if the piping springs up on release?
  • What if the load swings in my direction?

Knowing when a leak is happening is important to help keep employees safe. Gasket unloading is the most common reason for leaks. This is caused from a joint not able to generate enough seating stress on the gasket material. When gasket seating stress is low it can be from applying the wrong load to the gasket or the inability to transfer the correct load to the gasket from friction that is unaccounted for during tightening. To prevent these issues, a good bolting procedure should be in effect ASME PCC-1.

For other specific applications or general procedures, please contact the TFC applications engineer at [email protected] and read our Bolt Tightening Worksheet here.

Low Temperature Gaskets – How Low Can You Go?

June 6, 2019

By: Michael Pawlowski and Sylvia Flegg

Modern technology often requires rare or ultra-pure materials that can only be handled or obtained within extreme environmental conditions. These same conditions present unique and hazardous difficulties when transporting or utilizing these resources. Resources such as liquid oxygen, nitrogen, or argon; all of which are classified as “industrial gases” are handled well below the normal temperature ranges that every-day liquids exist; ranging as low as -195.8°C (-320.4°F).

As an example, let’s look at argon; an important gas used in Welding, Neon Lights, 3D Printing, and Metal Production, just to name a few. It is far more economical to house and transport argon in its liquid state. However, it must be held at an astonishingly low -185.9°C. Fitting the pipes together and maintaining a seal in a cryogenically engineered system that the liquid argon is housed presents unique difficulties. Argon gas is colourless, odourless, tasteless and can irritate the skin and the eyes on contact, and in its liquid form it can cause frostbite.


Proper Gasket Installation

Many gasket materials can become brittle, crack, shrink, and blow out when exposed to extreme cold – not something you want to happen at any time let alone with a liquid that can freeze you into a meatsicle. So, proper installation is also key! During installation, it is important that all parts are dry, the installation is done at ambient temperature and then re-adjusted with changes in temperature.



Any mechanical seal that is sealing a product with a temperature below 0 degrees Celsius is given the name “Cryogenic”. Liquefied gases (LNG), such as liquid nitrogen and liquid helium, are used in many cryogenic applications, as well as hydrocarbons with low freezing points, refrigerants and coolants.

When selecting a gasket or sealing material to be used in cryogenic service then it is important that the material can withstand cryogenic temperatures.

Low temperature applications are found across many industries, these include:

  • Chemical
  • Food
  • Pharmaceutical
  • Refrigeration
  • Petroleum
  • Automotive


Durlon® PTFE Gasket Material

A good material that can withstand the frigid cold and remain ductile is required to maintain the seal, and the standard go-to is polytetrafluoroethylene (PTFE). Durlon-9000’s low temperature threshold of -212 degrees centigrade makes it capable of withstanding the hostile environment demanded from handling ultra-cold and this glass filled PTFE is capable of resisting thermal contraction which otherwise might compromise the integrity of the seal.



As with all gasket applications, environmental conditions should be considered in conjunction with the functional requirements of the device. Learn more about our various Durlon PTFE products.

8 Steps to Properly Installing a Gasket

April 11, 2019

By Chett Norton, C.E.T. and Sylvia Flegg





Visually examine and clean flanges, bolts, nuts and washers and make sure to replace any defective components, if necessary.





Lubricate bolt threads, nut threads & facing, and washers.





Install new gasket (Do not reuse old gaskets or use multiple gaskets).





Number the bolts in a “cross pattern” sequence according to this diagram. Important: hand-tighten then pre-tighten bolts to 20 ft/lb torque but do not exceed 20% of target torque.






Check gap uniformity using a gap tool, feely gauge or Vernier calipers.





Target torque round #1 – 30% of target torque, Round #2 – 60% of target torque and round #3 – 100% of target torque. It is very important that you check the flange gap around the circumference in several spots between each of these tightening rounds. If the gap is not reasonably uniform, make the appropriate adjustments by selective bolt tightening before proceeding.





Rotational round: to reach 100% of the target torque, use a rotational clockwise tightening sequence starting with bolt 1 for one complete round and continue until no further nut rotation occurs at 100% of the target torque value for any nut.





Final-round: Re-torque within 4-24 hrs at ambient temperature if possible. Consult TFC technical department for hot-torquing procedures, repeat round 4 followed by a rotational round. A large percentage of short-term preload loss occurs within 24 hours after initial tightening this re-torquing round covers this loss and is especially important for PTFE gaskets.


We recommend the use of an installation assembly worksheet with the details of the assembly and installation including the installers signature and date for verification. You can use the TFC worksheet for easy adoption into your bolting installation verification program.


For other specific applications or general procedures, please contact the TFC applications engineer at [email protected] and you can read more about our Gasket Installation Procedures here.

Understanding Gasket Temperature and Pressure Limits

May 14, 2019

By Chett Norton, C.E.T.

When choosing the correct gasket material for a specific application, there are 3 minimum fields that you must understand in order to properly select the correct gasket:

  1. Pressure
  2. Temperature
  3. Media

All 3 of these items are straight forward on their own, however, most gasket applications are not based on 20°C or ambient test conditions in a lab so I will talk about each topic and how they interact with each other. The pressure is normally stated on the technical data sheet and refers to the pressure that the gasket is rated to at ambient temperature, so, for instance, Durlon® 8500 is rated for 1500psig at 20°C. Since soft gaskets are only recommended for both Class 150# & 300#, 1500psi seems adequate, right? Well if at ambient temperature, the max working pressure for a class 300# flange is 740psi for WCB piping/flanges and we used 1.5x this working pressure to cover system pressure tests, it would still only be 1140psig – still below the max allowable for the material. Unfortunately, it is not this simple.

What we sometimes fail to realize is that as the application temperature increases, the materials ability to withstand pressure decreases. Based on this, using a material’s Pressure vs. Temperature chart or referencing the materials PxT number are both quick tools that can be used to help verify if the material you have selected will work for the pressure and temperature conditions of your application. Many material tech sheets feature a “straight-forward” and easy-to-use PxT chart. The chart has a line that shows you a ‘go’ or ‘no-go’ area based on the pressure and temperature of the application for the material. Normally the pressure is listed on the Y-axis and the temperature is listed on the X-axis of the chart. Plotting the point at which these two values intersect will advise whether it is safe to use the material or not. If the point is inside the recommended line, it is generally safe to use, while being outside the line indicates not safe to use or recommends you contact engineering for more information. See the chart below for reference.


A second way to quickly check if the material is suitable for the application, is the PxT number. In some cases, the material-technical data sheet for the gasket material will give you a unit-less PxT number. For instance, Durlon 8500 material has a PxT (Psi x °F) value of 250,000 for 1/8″. Now what you can do is divide this number by either the working pressure or temperature (the number used to divide cannot exceed the max allowable temperature or pressure allowed for the material) and it will give you the maximum allowable of the variable not used. Allow me to give you an example:

Durlon 8500, PxT = 250,000

What is the maximum allowable pressure that the gasket can handle at 400°F?

250,000 / 400°F = 625 psi

Therefore, the maximum pressure the material can be used at 400°F is 625psi.

Additionally, media reactivity is also dependent on temperature. In a lot of cases, a materials chemical resistance at ambient temperature is good; however, at elevated temperature, the chemical is much more reactive and/or aggressive and renders the material not chemically compatible anymore. Therefore, it is very important when verifying chemical resistance, the temperature of the material needs to be taken into consideration besides the concentration of the media itself.

So, remember to verify these 3 items (Pressure, temperature, and media) and you can simplify it further by using the Durlon® iGasketPlus app to help recommend the correct material. So, play it safe, use the app and remember to always “Keep the fluid between the pipes”.

Blaming the Valve

March 4, 2019

By: Bruce Ellis

In many situations where a system starts to suddenly fail, the valve is the first suspect. This may or may not be true, depending on the issue. If a swing check valve is being used it is important to remember they are inherently noisy, so a quiet swing check is a problem. Whereas a non-slam check valve is designed to operate quietly, so if it becomes noisy, there is a problem.

Here are 3 questions to ask to help diagnose the issue causing system failure:

  1. Did the systems components change?

Simply put, is your pump or compressor working at the same efficiency (flow rate and pressure) as when it was new? Or did something change? It’s a good idea to have a pressure gauge and flow meter installed to monitor the conditions.

  1. Did something foreign enter the system?

Foreign objects sometimes find their way into a system causing damaged components, such as impellers and pistons. These objects can possibly get jammed in a valve, causing it to become stuck in the “open” or “closed” position. This can occur when intake screens become dislodged after repairs have been done, or on new installations. There have been documented occurrences where rocks, pieces of wood and even hand tools have been stuck in valves.

  1. Has there been a change in process conditions?

The media in a process can change. Is it more acidic? Does it contain more particulate? Did the specific gravity change? Any or all of the these will change how a valve operates. Increased acidity can cause failure of the spring and corrosion of the wetted parts. Increased particulate will cause faster wear of all parts and can lead to leaks and failure of a valve and other components in the system. A thicker than normal media will put strain on a pump and can slow the “close time” of a valve.

To help save money and down time, it is highly important to have an inspection and maintenance schedule to keep your system working properly and safely.

It’s all about efficiency!

Download the DFT® Silent Check Valve 6-page Brochure now!

Material Spotlight – PTFE (Polytetrafluoroethylene)

Feb 14, 2019

By: Michael Pawlowski, Laboratory Technologist

From interplanetary deep space missions to sealing the fittings between the faucets and pipes in your kitchen sink, Polytetrafluoroethylene (PTFE) can be found being used in almost every aspect of our daily lives. It was discovered accidentally April 6, 1938 by Dr. Roy J. Plunkett while running experiments utilizing gasses for freon refrigeration. The white waxy substance that had spontaneously polymerised was found to have some remarkable properties. PTFE turned out to be a resin impervious to almost every known solvent with a near frictionless surface which no substance would stick to.

The unique properties of PTFE lend itself well for use in a variety of industrial, manufacturing, and engineering facilities. The superb chemical resistance and tolerance to vast temperature gradients has not only improved the efficiency of many industries but the safety for the employees that work around those conditions as well.


  • Excellent chemical resistance
  • Wide range of service temperature
  • Excellent dielectric properties
  • Non-stick, low friction
  • No embrittlement or ageing
  • Smooth surface finish can be achieved
  • Non wetting
  • Outstanding corrosion protection
  • Electrical insulation
  • High thermal stability and flame resistance
  • Resistance to weathering
  • Food grade compliancy


Virgin PTFE
“Virgin PTFE” (PTFE without a filler) is one of the most chemically inert materials known and is used in many different applications and industries.

Glass Filled PTFE
Virgin PTFE with 25% Glass fiber filler which dramatically increases compressive strength and lowers deformation under load.

Bronze Filled PTFE
The addition of Bronze to PTFE gives better dimensional stability and lowers creep, cold flow and wear.

Carbon Filled PTFE
The addition of Carbon Fibre to PTFE increases the compressive strength and wear resistance. It provides good thermal conductivity and low permeability.

Stainless Steel Filled PTFE
The material is extremely hard wearing, has excellent strength and stability under extreme loads and elevated temperatures whilst still retaining the low coefficient of friction of conventional PTFE.


Because PTFE is a thermoplastic and due to its high viscosity, it cannot be processed using conventional polymer processing techniques. PTFE is processed by cold shaping and followed by heat treatment (sintering) during which polymer particles fuse to form a solid moulding.

PTFE is highly resistant to corrosion due to its chemical inertness. Unfortunately, that same chemical inertness prevents PTFE from being cross-linked like elastomers and is subject to the phenomenon of cold-flow – otherwise known as “creep”. To reduce and diminish cold-flow, additives are introduced during the preparation of PTFE compounds. Fillers, such as glass fiber found in Durlon® 9000 and 9000N gaskets, not only reduce creep but also maintain chemical inertness against aggressive and caustic chemicals but are still considered safe for use by food, drug and medical services.

Durlon® 9000 & 9000N PTFE SHEETS & GASKETS

Various shapes of inorganic fillers have been homogeneously blended with pure PTFE resins to give Durlon® 9000 its physical and mechanical properties. It is suitable for use in steel flanges and will not exhibit the cold flow problems associated with virgin PTFE or the hardness problems of some other filled PTFE products. It cuts easily and separates cleanly from flanges after use.

Durlon® 9000 – API Standard 6FA Fire Test, TA-Luft (VDI 2440), BAM, Pamphlet 95 (Chlorine Institute), FDA Compiant, USP Class VI Certified, ABS-PDA Certified, EC 1935/2004 Compliant, DNV-GL Accreditation, RoHS Reach Declaration

Durlon® 9000NFDA compliant, ABS-PDA Certified, USP Class VI Certified, RoHS Reach Declaration


Durlon® 9000 is made with Teflon™ fluoroplastic. Teflon™ is a trademark of The Chemours Company FC, LLC used under license by Triangle Fluid Controls Ltd.

It’s not me…it’s you!

Jan 31, 2019

By: Chett Norton, C.E.T.

I have had many conversations over the years with end users and installers, and the majority of the time, we realize that it wasn’t the gaskets fault for blowing. I often chuckle to myself wondering how the conversation would go if a gasket could talk to its end user? I think it would be very similar to the stereotypical relationship break-up line, “It’s me…it’s not you” but just the opposite, “It’s not me…it’s you” ‑ gasket talking to the end user.

Gasket failures are far too common and in a lot of cases can be categorized into 4 main categories – as this poll explains that was conducted by the FSA on 100 gasket failures. They determined the root cause of the failure causes as:

  • Under Compression (68%)
  • Over Compression (14%)
  • Wrong Product Used (14%)
  • Other (4%)

Under Compression can be caused by not tightening the bolt enough to apply the correct load on the gasket due to manual tightening or friction that is unaccounted for or possibly due to gasket relaxation. As you begin to tighten the material it will start to “creep” due to the compressive load being applied. As the gasket thickness decreases, the originally applied load on the bolts will lessen. This is due to the thickness change resulting in a lower gasket stress or compression and can cause a leak due to permeation through the gasket or tangential between the gasket and the flange sealing surface. Additionally, unloading of the gasket can occur due to temperature or pressure cycling which can have the same effect.

Over Compression is caused by too much load on the gasket. This can be caused by not using the correct torque value or perhaps using a tightening tool that you cannot measure the torque, for example an impact gun or cheater bar extension. Over compression reduces the contact area of the gasket and crushes the gasket towards the ID allowing fluid to penetrate the gasket ID thus leading to deterioration of the gasket, damaged flanges and can result in leakage or gasket failure ‑ a huge problem.

When Wrong Product is used, it can become a serious safety issue. The material selected must be capable for the temperature, pressure and media that it is being installed into. If the gasket material is not rated for either the pressure or temperature of the application, this can cause very serious issues such as worker injury or plant down time. Additionally, the gasket must be chemically compatible with the media or the chemical can attack the gasket; causing it to prematurely break down which may cause leakage or even failure.

And lastly, the Other category could be several things, such as using the incorrect gasket size, poor method of cutting, or quite simply, it is somewhat of anomaly and couldn’t be grouped into one of the three categories above.

The good news is, 96% of the above listed failures can be eliminated as they are in YOUR control! By following these few points, you can ensure that your gasket doesn’t have to give you “The Talk”.

  • Pick the correct material, verify the pressure, temperature and media that you will be installing the gasket into.
  • Use the proper tightening procedure noted in ASME PCCC-1.
  • Lubrication is key, friction is robbing and can account from more than 50% of the required torque.
  • Always use the manufacturers recommended torque values. If you are unsure, give them a call as they will be happy you did.
  • Use a proper tightening tool, such as torque wrench.
  • Gasket creep and bolt relaxation happens, be sure to eliminate this by always remembering to re-torque within 4-24 hrs.

So, the next time you have a gasket related issue, check to make sure it wasn’t due to one of the reasons mentioned above and remember to think to yourself WWTGGDWhat Would The Gasket Guru Do?

Until next time, keep the fluid between the pipes!

At Triangle Fluid Controls Ltd., we provide Gasket Installation Training to help prevent lost production time, to decrease maintenance costs, eliminate fines and to help ease your health and safety concerns.